1. Field of the Invention
The present invention relates to a walking beam type heat treatment apparatus configured to heat-treat a substrate such as a semiconductor substrate and a ceramics substrate.
2. Description of Related Art
There is known a heat treatment apparatus having a walking beam type substrate conveying device to convey using a walking beam in a heat treatment furnace configured to heat-treat a substrate such as semiconductor and ceramics ones. In such a heat treatment apparatus, the substrate is conveyed in the heat treatment furnace for drying or burning, and the heat treatment such as to form a layer by hardening a material on a surface (upper surface) and/or a back surface (lower surface) of the substrate is performed. For instance, JP 2003-176011 and JP 2004-18122 disclose such an apparatus.
The aforementioned heat treatment apparatus having the walking beam type substrate conveying device usually includes a first beam and a second beam that repeatedly alternate relative motions in the longitudinal and vertical directions of a heating furnace, a plurality of support pins respectively protruding upward from the first beam and second beam to support the substrate in contact with it. The substrate supported by the support pin on the lower surface is conveyed by delivering and receiving between the first and second beams.
The walking beam type heat treatment apparatus may require burning treatment to harden a material and form a layer on the upper surface and/or lower surface. For instance, on a solar cell substrate, a comb electrode material such as a thick layer material applied on the whole surface of one of the upper or lower surface in a predetermined pattern by printing, and a lower layer electrode material such as the similar thick layer material applied on the whole surface of the other of the upper or lower surface are burnt, to form the comb electrode and the lower layer electrode on one and the other of the upper and lower surfaces of the substrate.
However, in the conventional walking beam type heat treatment apparatus, for instance, in FIG. 9 a substrate 116 is supported by a support pin 126 of a first beam 120 and a plurality of support pins 124 respectively protruding upward from a second beam 122, the lower surface of the substrate 116 being in abutting contact with the support pins 124, 126. The substrate 116 is conveyed such that it delivered from the support pin 126 of the first beam 120 to the support pin 124 of the second beam 122. Accordingly, the applied layer of the lower surface of the substrate 116 is disadvantageously damaged mechanically upon burning because the material applied on the whole surface of the lower surface of the substrate 116 is contacted by the support pin 124.
It is therefore an object of the present invention to provide a walking beam type heat treatment apparatus in which the applied layer of the lower surface of the substrate is not contacted with the support pin.